1. Field of the Invention
The present invention relates in general to fuse holders and more particularly to a fuse holder having a sensor which provides a signal responsive to the magnetic field present when current is passing along the current path of the fuse holder.
2. Description of the Prior Art
As is well known, fuses for electric circuits are of numerous types and employ a fusible element which is enclosed in a suitable housing such as, for example, a cylinder of insulating material for preventing the component parts of the protectors from damage or deterioration. Additionally, the fuse housings are constructed of various sizes and shapes to be readily received in or removed from receptacles provided in the circuits with which the fuses are to be used.
When a large number of electrical circuits are provided in an installation, such as those in a large factory or on shipboard, it is extremely difficult for maintenance personnel to make the necessary tests of a number of fuses for the electric circuits before the particular protector that has acted to open a circuit may be located. Such testing is an extremely time consuming operation and is more or less a hit-or-miss proposition.
Various attempts have been made in the past to develop fuses for electric circuits which have indicators associated therewith in order to eliminate the necessity of manual inspection of the fuses. Some of these have been arranged to give an audible indication that a circuit has opened while others have provided for a visual indication of such a condition. One prior and commonly used indicating arrangement for visually showing that a fuse has blown and that a circuit is open has been to arrange a lamp and series resistor in the circuit, across the fuse, in such a manner that when the fused circuit was operating properly, the lamp and resistor would be shorted out but in the event that the circuit was overloaded to the extent that the fuse interrupted the circuit, a voltage would appear across the lamp to visually indicate this condition. Such a resistor/lamp arrangement has proved disadvantageous, for example, when the fuse blows, current will flow through the lamp and continue to flow through small load devices which the circuit is protecting, which may cause further breakdown in the circuit or device. Another known prior arrangement is shown in U.S. Pat. No. 3,158,713 titled Apparatus for Indicating an Open Electrical Circuit wherein a solenoid is wired in parallel with the electrical fuse which is actuated upon the fuse blowing to indicate that the fuse has operated to protect the circuit.
Another approach to indicating that an electric fuse has opened to protect an electrical circuit has been to provide an indicator in the fuse itself. Typically, such arrangements include a spring loaded pin or the like which is released to a visually ascertainable position upon the fuse blowing to protect the circuit. Such fuses are considerably more expensive than fuses not having such indicators and such a feature is particularly cost prohibitive in smaller low voltage class fuses.